Lightning-arrester.



Patented May 16, 1911.

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Inven tor E. E. P. GBEIGHTOH.

LIGHTNING ARRESTEE.

APPLICATION FILED FEBJ, 1907.

1 I I I [IL E. E. F. GREIGHTON. LIGHTNING ARRESTEE. APPLICATION FILEDFEB.7, 1907'.

992,744, Patented. May 16, 1911.,

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Elmer ELF Creico'hton,

SYW 8m x W W MW UNITED STATES PATENT OFFICE.

ELMER E. F. CREIGHTON, OF SGHENEOTADY, NEW YORK, ASSIGNOR TO GENERALELECTRIC COMPANY, A.

CORPORATION OF NEW YORK.

I To all whom it may concern:

Be it known that I, ELMER E.- F. CREIGH- TON, a citizen of the UnitedStates, residing at Schenectady, county of Schenectady, State of NewYork, have invented certain new and useful Improvements inLightning-Arresters, of which the following is a specification.

This invention relates to protective devices for electrical transmissionlines and more particularly to devices suitable for use on highpotential circuits.

- My invention includes several features which, though more or lessdistinct, cooperate to render the device reliable even under the tryingconditions imposed by modern practice in long distance and high voltagetransmission.

One feature of my invention resides in the use of duplicate devicesconnected to the same line-wire through spark gaps of diflerent lengthsand so arranged that if the charge to be conducted from the line isrelatively small, it will be passed over the shortest gap and throughonly one of the duplicate devices. If, however, the charge is heavy, andcould not be properly handled by a single device, it is permitted tobreak down a second spark gap and divide through a second device.

A second feature of my invention is an oil switch so arranged as tonormally complete the circuit between spark gaps and other elements ofthe protective device. This switch is arranged to break the circuitafter a heavy discharge has passed and to thereby disconnect thetransmission line from ground and prevent the line current fromfollowing through on any are formed by the escaping high potentialenergy. This switch automatically re-sets itself almost instantly, ashereinafter described more in detail.

A third feature of my'invention consists in the use of aluminumelectrolytic condensers or electrolytib cells of the aluminum type orabsorbing and transmitting energy of very high potential, and at thesame time opposing a practically prohibitive resistance to current ofnormal line potential.

The three more or less distinct elements above set forth are combinedwith each other and with the line circuits to be protected in such a waythat abnormal charges of almost any size and nature may be successfullyconducted to ground without danger of interrupting the service on thetransmission line Specification of Letters Patent. Application filedFebruary 7, 1907.

, Fig. 1, the

- adjunct to Patented May 16, 1911 Serial No. 356,149.

or of setting up dangerous oscillations, surges or fluctuations in theline potential.

In the drawings forming a part of this specification, I have illustratedthe various elements of the device and have indicated diagrammaticallyone arrangement of the elements suitable for protecting a threephasesystem.

Figure 1 isa diagrammatic illustration of my improved protective system;Fig. 2 is a sectional elevation of an aluminum condenser suitable foruse according to this invention; Fig. 3 is a side elevation of the oilbreak switch; and Fig. 4 is a transverse section thereof.

According to the arrangement shown in line conductors 1, 2 and 3 areconnected, respectively, through fused spark gaps 4, 5 and 6 to aplurality of spark gaps o varying sizes. Thus, conductor 1 is pro videdwith a main spark gap 8 adjusted to such a length that the normalpotential of the system will not send a discharge across the gap andmust be augmented by say ten per cent., before a spark will pass. Inparallel with this main gap 8 is a second circuit including a spark gap9 intended as an the main spark gap path and called into operation onlywhen the oil switch or other safety device of the main path is in theopen circuit position, as when rotating in the oil. Conductor 1 is alsoconnected to a third spark gap 7 having a length considerably greaterthan spark gap 8 and communicating with ground through an oil switch andan'electrolytic condenser. This path is intended as an emergency devicefor assisting the normal discharge path in carrying ofl" charges of verygreat quantity. In series with each of the gaps 7 8 and 9 is a horn gap10 shunted by a fuse l1 and connected in series with an automatic oilswitch 12. This switch comprises a tripping electromagnet 13 and aspring actuated rotary member 14 submerged in oil and connected by asliding contact with a brush 15. By means of this brush, connection ismade through a conductor 16 with other parts of the system. The trippingelectromagnet 13, which is necessarily inductive and acts much like areactance, is in parallel with an electrolytic condenser 17 of the typehereinafter described more in detail. This condenser provides a path forthe high potential discharges, entirely free from coils or windingswhich might tend to act as reactances for a current of high frequency.The duplicate oil switches in series with spark gaps 8 and 9 areconnected to conductor 18 leading to an electrolytic condenser 19 of thetype shown in detail in Fig. 2. This condenser is connected to groundthrough a spark gap 20 and a second condenser 21.

I have above described the paths to ground from conductor 1 of thethree-phase transmission line; conductors 2 and 3 are similarlyequipped. They arev provided respectively with condensers 22 and 23.These condensers are connected with electrolytic condenser 19 at thejunction point 24 leading 'to spark gap 20 of the ground connection. Theemergency paths through spark gaps 7 are provided with electrolyticcondensers 25, 26 and 27 similar in design to that shown in Fig. 2 buthaving a greater number of aluminum plates.

In order that the operation of my improved protective means may bebetter understood, reference is now had to the remaining figures whichillustrate details of,the electrolytic condensers and of the rotaryswitches.

Fig. 2 shows an oil tight box 25 provided with a cover carrying aninsulating bushing 26 through which passes a conductive standard 27serving as one terminal for the electrolytic condenser contained in thebox. The second terminal 28 passes through the bottom of the box and hasa cup-shaped depression in its top. A plurality of aluminum cups 29 arearranged between these two terminals. These cups may be frustoconical inshape and may be separated by saucer-like insulators 30. This particularshape of aluminum cup permits a ready discharge of the gases whichsometimes form during the operation-of an electrolytic condenser. Asuitable electrolyte 31, such as an aqueous solution of citric acid, isplaced between successive cups of the condenser or cell when theapparatus is set up, and the entire group of cups is then surroundedwith an insulating body of oil 32. As the separate cups are insulatedfrom each other except by the electrolyte placed therebetween, the cellas a whole may be regarded as a plurality of electrolytic condensersconnected in series. The condenser action of the aluminum electrolyticcell is usually attributed to the formation of a thin film of aluminumoxid or hydroxid on the aluminum plate. This film is due to theoxidizing action of the electrolyte when the aluminum p ate operates asanode. The film is of extreme thinness and seems to be partiallyabsorbed or eaten away from the plate when the condenser is inactive.Possibly it still remains, and this apparent absence is due to thesoaking up of the electrolyte by the film. The film does not appear tobe present when current first flows between the electrodes but isdeveloped only after the expenditure of considerable electrical energy.Thereafter it offers a high resistance to the flow of current from thealuminum plate. The film has,however, a break down voltage at which thefilm seems to puncture or fail in some way and lose its high resistancequalities. With an electrolyte of citric acid, the pressure betweenplates may be as high as 420 volts effective, before the film breaksdown and permits an appreciable current to flow between the plates. Notonly is the storage capacity of the aluminum condenser very high inproportion to its size and weight, but the condenser possesses certainother characteristics entirely lacking in condensers of ordinary type.The inductive capacity of the condenser bears a certain relation to theduration of the charging current; the capacity is, to a certain extent,dependent upon the time during which the condenser has been inoperation. When the condenser is first thrown in circuit, the leakagetherethrough is considerably higher than that found after the condenserhas been in operation for some little time. This phenomenon is probablydue to the gradual formation or development of the oxid or hydroxidcoating by the oxidizing action of the leakage current. When thecondenser is first thrown in circuit its low resistance or high leakagepermits a relatively large quantity of energy to pass during the firstinstant of operation and then by oxidation interposes a sufficientresistance to prevent excessive current from fiowing. In addition to thepeculiar features of the aluminum condenser above .set forth, itpossesses the characteristic of transmitting high frequency energy withmuch greater case than low frequency energy. This feature is allimportant in the use of these electrolytic condensers, for when thecondensers are properly connected they act as selective devices to carryoff the high frequency potential without permitting the normal currentof the line to follow through on the high potential discharge.

Figs. 3 and 4 illustrate the rotary oil switch indicateddiagrammatically in Fig. 1. This switch comprises an oil tight boxwithin which is mounted a spring actuated rotary member 14 consisting offour radial arms mounted on a hub 33. A coiled spring 34: is secured tothe hub and may be put under tension by means of a string 35 wound in aspiral groove of the hub and passing upward through the cover of thebox. When the spring is under tension it tends to rotate the hub in aclockwise direction and holds the radial arms in electrical contact witha tripping plunger 36. This plunger not only holds the rotating member14: against rotation by the spring but also serves to conduct current toone of the radial 2. In a protective device for electrical sysarms asshown diagrammatically in Fig. 1., terns, a ground connection, aplurality of 50 The radial arms are electrically connected electrolyticcondensers connected therewith, through the hub with a slip ring onwhich a plurality of automatic switches in series the brush 15 makes asliding contact. The with said condensers,-a line conductor, andtripping plunger is controlled by an electroa plurality of spark gaps ofdifferent magnet 13 and may be lifted to release one lengths interposedbetween said conductor 55 of the rotary arms and open the circuit andsaid automatic switches. under the oil. 3. In an electrical protectivedevice, a When the above described oil switch and switch comprising arotary member subelectr'olytic condenser are assembled as merged in oil,a tripping means therefor shown in Fig. 1, they constitute protectiveactuated by an electromagnet, a condenser 60 means of good e money. Whenthe quanin shunt with said electromagnet, and an tity of energy to bedischarged from the line 15 is not too large 1t is absorbed in theelectro- 4. The combination with a line conductor chemical action whichtakes place in the con-' maximum or break down voltage of the condenserand the line is relieved of its hi h potential without any disturbanceof t a normal line current. If the plate surface of the cell is notsufiicient to absorb all the disharge, the voltage rises above thecritical lm voltage and the film breaks and the film resistance drops toasmall fraction of its maximum value; current then flows freely throughthe cell. As soon, however, as the voltage drops below the critical orbreak down voltage the film resistance reappears and chokes down thecurrent to a low value. The oil switches in series with the electrolyticcondensers serve to interrupt the condenser current which flows in theelectrolytic cell after the main line discharge has passed. What Iclaim. as new and desire to secure by Letters Patent of the UnitedStates, 1s,- l. The combination with a line conductor to be protectedfrom high potential charges, a plurality of paths to ground therefor,spark gaps of different lengths for said paths, an oil switch in each ofsaid paths, an electrolytic condenser common to a plurality of saidpaths, electromagnetic means Witnesses: for tripping said switchesandcondensers BENJAMIN B. HULL, in shunt with said electromagneticmeans. HELEN Onronn.

electrolytic condenser, and a second path to ground therefor having alarger spark pspark gap, an aluminum electrolytic condenser in serieswith said spark gap, and an automatic switch for rupturing the condensercurrent after a discharge has passed therethrough.

6. Protective means for an electrical sys tem, comprising a groundconnection, an electrolytic condenser connected therewith and parallelpaths between said condenser and a line conductor, each of said paths soincluding a rotary oil switch.

v The combination of a plurality of line conductors, a path to groundfor each of said conductors including a relatively large spark gap andan electrolytic condenser, and a second path to ground for each of saidconductors, said second path including an electrolytic condenser inseries with a plurality of automatic switches.

my hand this 5th day of February, 1907. ELMER E. F. OREIGI-ITON.

a path to ground therefor including a 5 5. In an electrical protectivedevice, a 70' In witness whereof, I have hereunto set v

